New research published in Physical Review Letters has ruled out stupendously large
primordial black holes as a significant source of dark matter.
The study, conducted by researchers at Johannes Gutenberg University Mainz (JGU), analyzed measurements of the cosmic microwave background (CMB) from the European Space Agency’s Planck satellite, which operated until October 2013.
The team found that if these immense black holes had existed in large numbers, they would have left a distinct, “grainy” imprint on the CMB. However, the actual Planck data shows no such pattern, effectively ruling them out as a major component of dark matter.
The research was published in Physical Review Letters. The study was authored by Gerlach, Gouttenoire, Iovino, and Leister.
The cosmic microwave background measurements by the Planck satellite show no evidence of stupendously large black holes formed shortly after the Big Bang to contain significant amounts of dark matter. While physicists today know that dark matter must exist, there are still many unanswered questions surrounding it – such as what it is made of.
What Are Stupendously Large Black Holes?
Primordial black holes are theoretical objects that could have formed directly from dense clumps of matter in the very early universe, long before the first stars. Stupendously large
black holes, or SLABs, are a specific subset of these theoretical objects, each weighing at least 100 billion times the mass of the sun—more massive than the largest supermassive black holes known today.
The CMB is the light released when the universe was just 380,000 years old. To measure it, one must bring highly specialized equipment and leave the Earth’s atmosphere. Its measurements allow more precise calculations of the universe’s visible and dark matter contents.
Analysis of primordial black holes, which were formed shortly after the Big Bang, has already shown that they are unlikely to have contained all dark matter in the universe.
The JGU research team studied stupendously large black holes (SLABs), which were candidates for containing much or all dark matter. Their research has been published in Physical Review Letters.
The team calculated that if such objects existed in sufficient numbers to account for dark matter, their gravitational influence would have left a distinct, enlarged imprint on the cosmic microwave background radiation. Current observations of the cosmic microwave background by missions such as Planck show no evidence of this predicted distortion. Not enough graininess was found, ruling out the possibility of SLABs as significant parts of dark matter.
Findings Narrow Potential Dark Matter Explanations
The finding narrows the field of potential explanations for dark matter. The result narrows the parameter space for what dark matter could be, directing future searches toward particle-based explanations or other exotic physics.
The study also challenges the idea that SLABs could have helped seed the surprisingly massive early galaxies observed by the James Webb Space Telescope. One of the phenomena these objects were theorized to explain is the nano-Hertz gravitational-wave background, or “hum” detected in Pulsar Timing Arrays, another are the surprisingly large early galaxies observed by the James Webb telescope.
These questions are also unlikely to be answered by SLABs, since our findings show that they didn’t exist in large numbers,
said Nicholas Leister, another JGU physicist in the research team. The early universe still has many puzzles waiting to be solved.
While the research definitively closes one door, it leaves others open for future investigation. The finding represents a step forward in the process of elimination that characterizes much of modern dark matter research.
Dark matter remains one of the primary unsolved problems in cosmology, constituting roughly 85% of the matter in the universe while emitting no light.
